Experimental and statistical approaches in method cross-validation to support pharmacokinetic decisions

Area of Science:

• Pharmacokinetics
• Bioanalytical Method Validation

Background:

• Ligand binding assays (LBAs) are essential in pharmacokinetic (PK) studies.
• Changes in bioanalytical methods require rigorous cross-validation to ensure data consistency.
• Equivalence criteria are critical for comparing different assay methodologies.

Purpose of the Study:

• To present experimental and statistical approaches for cross-validating two LBAs used in PK studies.
• To assess the impact of methodological changes on PK data interpretation.
• To determine if two LBAs were statistically equivalent based on predefined criteria.

Main Methods:

• Cross-validation involved experimental design, sample size selection, and statistical analysis.
• Method equivalence was defined by a 90% confidence interval (CI) for the mean concentration ratio within 0.80-1.25.
• Analysis of variance (ANOVA) was used to compute the difference of log-transformed mean concentrations and 90% CIs.

Main Results:

• The mean concentration ratios for incurred and spiked samples were 1.63 and 1.57, respectively.
• The 90% CIs for these ratios (1.55-1.72 and 1.54-1.60) fell outside the 0.80-1.25 equivalence interval.
• Pharmacokinetic parameters (AUC(0-168) and Cmax) differed approximately twofold between studies using the two methods.

Conclusions:

• The two LBA methods were not statistically equivalent.
• The lack of equivalence significantly impacted PK parameters, demonstrating a twofold difference in therapeutic exposure.
• This study underscores the necessity of method cross-validation when altering bioanalytical methods or statistical approaches in PK studies.